全文获取类型
收费全文 | 23771篇 |
免费 | 5157篇 |
国内免费 | 8164篇 |
专业分类
化学 | 17688篇 |
晶体学 | 1159篇 |
力学 | 1718篇 |
综合类 | 966篇 |
数学 | 3693篇 |
物理学 | 11868篇 |
出版年
2024年 | 66篇 |
2023年 | 266篇 |
2022年 | 876篇 |
2021年 | 870篇 |
2020年 | 902篇 |
2019年 | 892篇 |
2018年 | 818篇 |
2017年 | 1097篇 |
2016年 | 952篇 |
2015年 | 1306篇 |
2014年 | 1456篇 |
2013年 | 2019篇 |
2012年 | 2051篇 |
2011年 | 2105篇 |
2010年 | 1969篇 |
2009年 | 2135篇 |
2008年 | 2412篇 |
2007年 | 2059篇 |
2006年 | 1952篇 |
2005年 | 1679篇 |
2004年 | 1375篇 |
2003年 | 1021篇 |
2002年 | 936篇 |
2001年 | 994篇 |
2000年 | 1031篇 |
1999年 | 665篇 |
1998年 | 344篇 |
1997年 | 295篇 |
1996年 | 322篇 |
1995年 | 300篇 |
1994年 | 248篇 |
1993年 | 244篇 |
1992年 | 192篇 |
1991年 | 159篇 |
1990年 | 159篇 |
1989年 | 164篇 |
1988年 | 129篇 |
1987年 | 105篇 |
1986年 | 84篇 |
1985年 | 57篇 |
1984年 | 78篇 |
1983年 | 78篇 |
1982年 | 66篇 |
1981年 | 49篇 |
1980年 | 40篇 |
1979年 | 28篇 |
1978年 | 13篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1959年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Qipeng Guo Fei Chen Ke Wang Ling Chen 《Journal of Polymer Science.Polymer Physics》2006,44(21):3042-3052
An amphiphilic poly(ethylene oxide)‐block‐poly(dimethylsiloxane) (PEO–PDMS) diblock copolymer was used to template a bisphenol A type epoxy resin (ER); nanostructured thermoset blends of ER and PEO–PDMS were prepared with 4,4′‐methylenedianiline (MDA) as the curing agent. The phase behavior, crystallization, hydrogen‐bonding interactions, and nanoscale structures were investigated with differential scanning calorimetry, Fourier transform infrared spectroscopy, transmission electron microscopy, and small‐angle X‐ray scattering. The uncured ER was miscible with the poly(ethylene oxide) block of PEO–PDMS, and the uncured blends were not macroscopically phase‐separated. Macroscopic phase separation took place in the MDA‐cured ER/PEO–PDMS blends containing 60–80 wt % PEO–PDMS diblock copolymer. However, the composition‐dependent nanostructures were formed in the cured blends with 10–50 wt % PEO–PDMS, which did not show macroscopic phase separation. The poly(dimethylsiloxane) microdomains with sizes of 10–20 nm were dispersed in a continuous ER‐rich phase; the average distance between the neighboring microdomains was in the range of 20–50 nm. The miscibility between the cured ER and the poly(ethylene oxide) block of PEO–PDMS was ascribed to the favorable hydrogen‐bonding interaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3042–3052, 2006 相似文献
2.
3.
4.
1 INTRODUCTION Carbon nanotubes have many potential applica- tions due to their unique structures and properties[1~4]. Physicists have been studying their electrical, me- chanical and other properties since their discove- ries[5, 6]. Recently, chemists are interested in carbon nanotubes because their properties can be altered by chemical functionalization[7~14], and these functiona- lized nanotubes can undergo further chemical trea- tment. So the potential application range of such na- … 相似文献
5.
激光等离子体探针及应用研究 总被引:6,自引:1,他引:5
本文介绍用阴影、纹影相干涉方法确定等离子体折射系数变化的原理。分析了等离子体中的非线性效应和对光探测系统的基本要求。并简要叙述了实验上采用的后向喇曼探测束,给出了等离子体干涉、纹影和阴影的测量结果。 相似文献
6.
Fei Chang Dongheng Zhang Haijian Yang Haibin Song 《Journal of organometallic chemistry》2004,689(5):936-946
The synthesized 1-aryliminomethylenylnaphthalen-2-ol derivatives reacted with nickel chloride to form bis(1-aryliminomethylenylnaphthalen-2-oxy)nickel complexes. All resultant compounds were structurally characterized by elemental analyses, IR and H NMR, and the structures of the formed complexes were elucidated by X-ray crystal structure analysis. The complexes show high catalytic activities for the vinyl polymerization of norbornene in the presence of methylaluminoxane. The catalytic activity variations have been followed by gas chromatography through monitoring the conversion of norbornene. 相似文献
7.
Herein we report a new method to collect a qualified infrared spectrum of a solute in solution by two solvent cells with different thickness during background single-beam spectrum scanning. By collecting the background spectrum with two cells (two stages), we successfully achieved accurate solvent compensation between a sample and a reference, namely, the solvent amounts in the sample and background measurements could become congruent. Therefore, the solvent bands were thoroughly suppressed in the infrared spectrum and a qualified spectrum of the solute was obtained. 相似文献
8.
在组合系统运用Kalman滤波器技术时,准确的系统模型和可靠的观测数据是保证其性能的重要因素,否则将大大降低Kalman滤波器的估计精度,甚至导致滤波器发散.为解决上述Kalman应用中的实际问题,提出了一种新颖的基于进化人工神经网络技术的自适应Kalman滤波器.仿真试验表明该算法可以在系统模型不准确时、甚至外部观测数据短暂中断时,仍能保证Kalman滤波器的性能. 相似文献
9.
10.